Hand held, hand-actuated suction pumps are generally known. Classically they include a plunger inside a cylinder and some arrangement of two serially connected check valves. One of the check valves enables air to be withdrawn from a region to be evacuated and prevents reverse flow into that region. The other of the check valves enables air to be drawn into the cylinder through the first check valve, and passes air to be discharged to the atmosphere without returning it to its source.
In view of the long history and simplicity of such pumps and of their wide application, it is surprising that unmet objectives continue to exist. But they do, and this invention was made to meet some of them.
For example most suction pumps have rather complicated check valves that can easily be clogged up by particulate material. When such pumps are used in agricultural work, they break down too readily. It is an object of this invention to provide a rugged suction pump that can be assembled from simple parts, which is not as subject to clogging up, and whose most critical parts can inexpensively be formed by molding processes.